Electrical connection for burglar-alarms



(No Model.)

J. A. DAVIS. BLEGTRIGAL CONNECTION FOR BURGLAR ALARMS.

No. 259,82 5' Patented June 20,1882.

FIGQZ.

FlG.-3

INVENTOR aff/fax;

N. PETERS, Pbolo-Lhhognpher. Washington. 5.6-

UNITED STATES PATENT OFFICE.

JOB A. DAVIS, OF PHILADELPHIA, PENNSYLVANIA.

ELECTRICAL CONNECTION FOR BURGLAR-ALARMS.

SPECIFICATION forming part of Letters Patent No. 259,825, dated June 20,1882.

Application filed November 11, 1881. (No model.)

To all whom it may concern Be it known that I, JOB A. DAVIS, of the cityand county of Philadelphia, in the -State plicable within a smallcompass to the duty of opening or closing an electrical circuit inconnection with a burglar-alarm.

To this end my improvements consist in the combination of parts orelements, as hereinafter morefully set forth.

In the accompanying drawings, Figure 1 is a view in perspective of anelectrical connection embodying'my invention, and Figs. 2 and 3longitudinal central sections of the same, showing respectively itsadaptation to an open and to a closed circuit.

The base-plate A is made fiat upon one of its sides, adjacent to eachend of which is formeda tapered or countersunk hole, a, through whichholes pass the screws by which the plate is secured to the door orwindow frame upon which it is to-be located. The plate A is swelled orthickened toward each end, so as to form seats or bearings b b for twoflexible contact-plates, B B, of metal, each of which is secured at oneend to its seat by screws bZ'and is free from fixed bearing at the otherend, which projects downwardly into the space or recess between theseats or bearings, one of which-in this case the seat b of the plateB-must be formed of some insulating material, so as to obviate thedirect passage of an electrical current from the seat to the plate, orvice versa. A stem, 0, is fitted in a central opening in the base-plateA, so as to have the capacity'of movement therein'at right angles to thefaces of the seats b b, and is connected to the projecting end of theplate B, so that the latter shall partake of the movements of the stem.This I accomplish by forming a central recess in the contact-plate andfitting the edges of the contact-plate on each side of said recess intogrooves c on the stem 0. A spring, D, secured to the seat b of thecontact-plate B,

presses the latter and the connected stem Gin the direction of the flatface of the base-plate A, andtretains them in the position shown in thedrawings, except when opposed by a pressure in the opposite directionsufiicie'nt to overcome its resilience. The spring may be dispensed withif the elasticity of the plate B is sufficient to produce an equivalentresult. Wires E and F for the passage of an electrical current areconnected to the contact-plates B and B, respectively, the circuit ofsuch current being, as will be apparent, closed when the free ends ofthe plates B and B are in contact, and open when they are not. 7

As shown in Fig. 2, the device is arranged for operation with a circuitwhich is normally open, and upon the closing of the circuit, which willbe effected by the inward movement of the stem 0 and contactplate B,caused by the pressure of the door or windo'win being opened, the alarmwill be sounded. A corresponding result will be attained when the platesare arranged for operation with a normally closed circuit, as in Fig. 3,the breaking of which circuit will be similarly effected by the inwardmovement of the stem 0 and contact-plate B.

It will be seen that the arrangement of parts is such that the entiredevice occupies but a comparatively small compass; and, further, that itmay be readily adjusted to either an open or a closed circuit by causingthe free end of the contact-plate B to occupy a position either below orabove that of the plate B, as the case may be. Such adjustment iseffected by removing one of the holding-screws b? of the plate B,turning the plate upon the 13, connected with the groove 0 of the stem0,

all combined and operating substantially as and for the purpose setforth.

JOB A. DAVIS.

Witnesses: 7

J. SNowDEN BELL, GEO. 'l. KELLY.

